Abstract:

The present invention, in one set of embodiments, provides methods and
systems for integrating conducting diamond electrodes into a high power
acoustic resonator. More specifically, but not by way of limitation, in
certain embodiments of the present invention, diamond electrodes may be
integrated into a high power acoustic resonator to provide a robust
sensing device that may provide for acoustic cleaning of the electrodes
and increasing the rate of mass transport to the diamond electrodes. The
diamond electrodes may be used as working, reference or counter
electrodes or a combination of two or more of such electrodes. In certain
aspects, the high power acoustic resonator may include an acoustic horn
for focusing acoustic energy and the diamond electrodes may be coupled
with the acoustic horn.

Claims:

1. A method for obtaining electrochemical measurements from a substance
using an erosion and wear resistant sonoelectrochemical probe:contacting
a first electrode and a second electrode of the sonoelectrochemical probe
with the substance, wherein the sonoelectrochemical probe comprises a
high power acoustic resonator with an acoustic horn and the first and
second electrodes are disposed at one end of the acoustic horn;using the
high power acoustic resonator to generate acoustic energy; andmeasuring
electrical properties of an electrical current flowing between the first
diamond electrode and the second electrode.

2. The method of claim 1, wherein the first and second electrodes comprise
doped diamond electrodes and the first diamond electrode and the second
electrode are disposed in a single diamond substrate.

3. The method of claim 1, wherein the first electrode comprises a working
electrode and the second electrode comprises a reference electrode.

4. The method of claim 1, further comprising contacting a third electrode
with the substance.

5. The method of claim 4, wherein the third electrode comprises a counter
electrode.

6. The method of claim 4, wherein the first, second and third electrodes
comprise diamond doped electrodes and are disposed in a single diamond
substrate.

7. The method of claim 1, wherein the acoustic energy generated by the
high power acoustic resonator is used to provide for cleaning of the
first and second electrodes.

8. The method of claim 1, wherein the step of using the high power
acoustic resonator to generate acoustic energy comprises longitudinally
oscillating the acoustic horn.

9. The method of claim 1, wherein the first and second electrodes comprise
diamond doped with an n-type or p-type dopant.

10. The method of claim 1, wherein the first and second electrodes
comprises boron-doped diamond.

11. The method of claim 1, wherein the first and the second electrode are
separated by electrically non-conducting diamond.

12. The method of claim 1, wherein the first and the second electrode
comprise a macroscopic array of electrically conducting diamond regions
separated by electrically non-conducting diamond regions.

12. The method of claim 1, wherein the first and the second electrode
comprise a macroscopic array comprises a central disc of boron-doped
diamond, a first plurality of concentric rings of electrically
non-conducting diamond and a second concentric ring or plurality of
concentric rings of boron-doped diamond.

13. The method of claim 1, further comprising:using the acoustic energy to
mix the substance.

14. The method of claim 13, further comprising:taking electrical
measurements from the first and second electrodes.

15. The method of claim 1, further comprising:taking electrical
measurements from the first and second electrode while the acoustic
energy is applied to the substance.

Description:

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001]This application is a divisional of U.S. application Ser. No.
11/499,332, filed on Aug. 4, 2006 entitled "Erosion and Wear Resistant
Sonoelectrochemical Probe", which is related to U.S. application Ser. No.
11/499,329, filed on Aug. 4, 2006, entitled "High Power Acoustic
Resonator with Integrated Optical Interfacial Elements." These
applications are also related to the following commonly-owned patents,
U.S. Pat. No. 6,880,402 ("the '402 patent) to Couet et al., U.S. Pat. No.
6,886,406 ("the '406 patent) to Couet et al., and U.S. Pat. No. 6,995,360
("the '360 patent") of which the entire disclosure of each is hereby
incorporated by reference for all purposes.

BACKGROUND OF THE INVENTION

[0002]Combining high power ultrasound and electrochemical analysis
functions and properties has most often previously been achieved by
configuring a high power acoustic resonator and separate electrode system
in a face-on geometry. In such an arrangement, the spacing between the
electrode and acoustic resonator can be varied to vary the effect of the
separated acoustic and electrode systems. However, it should be noted,
that the spacing between the acoustic resonator and the electrode system
in the face-on geometry will result in a decrease in the electrode
cleaning capabilities of the acoustic resonator and the mass transfer
rate associated with the electrode when operated contemporaneously with
the acoustic resonator. Furthermore, investigations with regard to
performance of such face-on configurations identified the existence of
wear and erosion issues associated with the systems

[0003]In another arrangement configured to provide for combined ultrasound
and electrochemical analysis functions and properties, an acoustic horn
of a high power acoustic resonator has itself been used as an electrode.
In these configurations, the acoustic horn itself is used as the working
electrode in an electrochemical circuit. J. Reisse et al. in an article
entitled "SONOELECTROCHEMISTRY IN AQUEOUS ELECTROLYTE: A NEW TYPE OF
SONOELECTROREACTOR", Electrochim. Acta, 39, 37-39 (1994), disclose using
a titanium ultrasonic horn as a working electrode to provide for
depositing copper from a solution of copper sulphate in the presence of
high power ultrasound at a frequency of 20 kHz. Durant et al. describe
using a titanium horn as the working electrode to study the effects of
high power ultrasound on the electrochemical reduction of benzaldehyde
and benzoquinone. (Durant, A., Francois, H., Reisse, J. and Kirsch-de
Mesmaeker, A., "SONOELECTROCHEMISTRY: THE EFFECTS OF ULTRASOUND ON
ORGANIC ELECTROCHEMICAL REDUCTION", Electrochim. Acta, 41, 277-284
(1996).

[0004]Other arrangements provide for attaching the electrode to an
acoustic horn. Such an arrangement may be termed a sonotrode and such a
device is available commercially from Windsor Scientific. The Windsor
Scientific sonotrode consists of a glassy carbon disk electrode set in
the end of a quartz rod, wherein the quartz rod is screwed into the end
of an ultrasonic horn. Although the sonotrode is a combined system with
the acoustic resonator and electrode combined, the electrode is still
disposed distally from the acoustic horn; so as with the face-on
geometry, the separation will result in a decrease in the electrode
cleaning capabilities of the acoustic resonator and the mass transfer
rate associated with the electrode when operated contemporaneously with
the acoustic resonator. Further, the Windsor Scientific sonotrode does
not provide a rugged and wear/erosion resistant design and may not be
capable of operating at high acoustic powers and/or may experience
degradation of the glassy carbon disk electrode under acoustic functions.
In another sonotrode-type device, A. O., Simm et al. "SONICALLY ASSISTED
ELECTROANALYTICAL DETECTION OF ULTRATRACE ARSENIC", Anal. Chem., 76,
5051-5055 (2004), an electrode may be attached to a small permanent
magnet that may be made to vibrate by passing current through an adjacent
electric coil.

[0005]In a further acoustic resonator and electrode arrangement, modifying
the idea of using the acoustic horn as the electrode, a platinum
electrode is disclosed that is bonded into a hole drilled in the titanium
tip of an acoustic horn using an adhesive. (R. G. Compton, et al.,
"ELECTRODE PROCESSES AT THE SURFACE OF SONOTRODES", Electrochim. Acta,
41, 315-320 (1996)). In such an arrangement, as with arrangements wherein
the acoustic horn acts as an electrode, the distance between the
electrode and the acoustic horn does not become an issue. In the
electro-acoustic system disclosed by Compton, electrical connections to
the platinum electrode are provided by wire connections passing through
the side of the acoustic horn to the platinum electrode. While the
reference provides a sonotrode that effectively addresses issues
regarding separation of the acoustic resonator and the electrode it does
not address using acoustic energy to clean the electrode or provide for
effectively configuring the acoustic resonator and electrode system for
combined operation. Furthermore, the reference does not disclose a
sonotrode that may be suited for remote operation, operation in harsh
environments--including high temperatures or pressures--or that can be
effectively used repeatedly at high acoustic energy levels.

BRIEF SUMMARY OF THE INVENTION

[0006]Embodiments of the present invention relate to integrating an
electrode system with a high power acoustic resonator. More specifically,
but not by way of limitation, embodiments of the present invention
provide for integrating a diamond electrode with the high power acoustic
resonator to provide a sonoelectrochemical interface that is erosion and
wear resistant that may be used in fouling and harsh environments and is
capable of remote operation. Additionally, in certain embodiments of the
present invention, by integrating the electrode system into an acoustic
horn of the acoustic resonator the system may provide for effective
cleaning of the electrode and effective operation of the
sonoelectrochemical interface at high acoustic energies.

[0007]In one embodiment, an erosion and wear resistant sonoelectrochemical
probe configured for high power ultrasonic operation is provided
comprising a high power acoustic resonator with an acoustic body and a
transducer coupled to the base of the acoustic body, a diamond electrode
coupled with a tip of the acoustic body and an electrically conducting
element coupled with the diamond electrode. In one aspect of the
invention, the diamond electrode may be a diamond microelectrode array.
In certain aspects, the electrically conducting element may be disposed
within the acoustic body so that it passes from the tip of the acoustic
body and through the base of the acoustic body. Disposing the
electrically conducting element inside the acoustic body may provide for
a sonoelectrochemical probe that may be used in extreme conditions and/or
for effective operation of the acoustic resonator at high powers with the
combined electrode system.

[0008]The diamond electrode may comprise a boron-doped diamond. In certain
aspects, the boron-doped diamond electrode may be configured so that
there is a central disc of boron-doped diamond surrounded by a concentric
ring of non-conducting diamond, wherein the concentric ring of
electrically non-conducting diamond provides for the insulation of the
central disc of the boron-doped diamond from the acoustic body. In
further embodiments of the present invention, the diamond electrode may
comprise a macroscopic and/or a microscopic array formed from boron-doped
diamond regions and electrically non-conducting diamond regions. In
certain aspects, the boron-doped diamond regions and electrically
non-conducting diamond regions may be arranged in concentric rings around
a central disc of boron-doped diamond. In the array and ring-type
configurations of the non-conducting and electrically conducting diamond,
the individual electrodes of the sonoelectrochemical probe formed by the
electrically isolated regions of the electrically conducting diamond may
be configured to provide working, counter and reference electrodes. In
such configurations, the sonoelectrochemical probe may comprise a
complete and robust, integrated system for performing
sonoelectrochemistry measurements.

[0009]In an embodiment of the present invention, the rugged and wear
resistant sonoelectrochemical probe may be contacted with a substance or
the substance may be made to contact the sonoelectrochemical probe, a
second electrode may also be contacted with the substance, the high power
acoustic resonator may be used to generate acoustic energy and electrical
properties of an electrical current flowing between sonoelectrochemical
probe and the second electrode may be measured. Further, a third
electrode may also be contacted with the substance. The second electrode
may be coupled with the sonoelectrochemical probe to provide an
integrated system for taking sonoelectrochemical measurements. Yet
further, the third electrode may be coupled with the sonoelectrochemical
probe and the second electrode to provide a three electrode integrated
system for taking sonoelectrochemical measurement using the working,
reference and counter electrode system well know to those skilled in the
art. In other aspects, multiple electrodes may be formed on the active
face of the sonoelectrochemical probe by the creation of regions of
electrically conducting diamond on the electrode surface of the
sonoelectrochemical probe, electrically insulated from each other. In
certain aspects, these electrically isolated regions may be areas of
electrically conducting diamond surrounded by non-conducting diamond, and
these multiple electrodes may be used as working and reference electrodes
and/or counter electrodes. In certain aspects, the high power acoustic
resonator may be used to generate acoustic energy to clean the
sonoelectrochemical probe and/or to mix the substance or substances in
contact with the sonoelectrochemical probe.

[0010]Further areas of applicability of the present invention will become
apparent from the detailed description provided hereinafter. It should be
understood that the detailed description and specific examples, while
indicating various embodiments of the invention, are intended for
purposes of illustration only and are not intended to limit the scope of
the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011]In the figures, similar components and/or features may have the same
reference label. Further, various components of the same type may be
distinguished by following the reference label by a dash and a second
label that distinguishes among the similar components. If only the first
reference label is used in the specification, the description is
applicable to any one of the similar components having the same first
reference label irrespective of the second reference label.

[0012]The present invention will become more fully understood from the
detailed description and the accompanying drawings, wherein:

[0013]FIG. 1 is a schematic type illustration of a high power acoustic
resonator that may be used in an embodiment of the present invention;

[0014]FIG. 2 is a schematic-type diagram illustrating a high power
acoustic resonator with an integrated electrically conducting diamond
electrode, in accordance with an embodiment of the present invention;

[0015]FIG. 3 is a schematic-type diagram illustrating a high power
acoustic resonator with an integrated diamond electrode comprising a
plurality of conducting regions separated by non-conducting regions that
may be used as reference or counter electrodes and working electrodes, in
accordance with an embodiment of the present invention; and

[0016]FIG. 4 is a schematic-type diagram illustrating a high power
acoustic resonator with an integrated diamond electrode array, in
accordance with an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0017]The ensuing description provides preferred exemplary embodiment(s)
only, and is not intended to limit the scope, applicability or
configuration of the invention. Rather, the ensuing description of the
preferred exemplary embodiment(s) will provide those skilled in the art
with an enabling description for implementing a preferred exemplary
embodiment of the invention. It being understood that various changes may
be made in the function and arrangement of elements without departing
from the spirit and scope of the invention as set forth in the appended
claims.

[0018]Specific details are given in the following description to provide a
thorough understanding of the embodiments. However, it will be understood
by one of ordinary skill in the art that the embodiments maybe practiced
without these specific details. For example, circuits may be shown in
block diagrams in order not to obscure the embodiments in unnecessary
detail. In other instances, well-known circuits, processes, algorithms,
structures, and techniques may be shown without unnecessary detail in
order to avoid obscuring the embodiments.

[0019]Also, it is noted that the embodiments may be described as a process
which is depicted as a flowchart, a flow diagram, a data flow diagram, a
structure diagram, or a block diagram. Although a flowchart may describe
the operations as a sequential process, many of the operations can be
performed in parallel or concurrently. In addition, the order of the
operations may be re-arranged. A process is terminated when its
operations are completed, but could have additional steps not included in
the figure. A process may correspond to a method, a function, a
procedure, a subroutine, a subprogram, etc. When a process corresponds to
a function, its termination corresponds to a return of the function to
the calling function or the main function.

[0020]Interest in the combination of high power ultrasound and
electrochemical analysis has developed based upon an understanding of the
advantages of using high power ultrasound when making electrochemical
measurements and the term sonoelectrochemistry has been coined to
describe the union of high power ultrasound and electrochemical
measurements. In particular, two advantages have been observed in the use
of high power ultrasound with electrochemical measurements.

[0021]With regard to the first advantage, it has been found that the use
of ultrasound significantly increases the rates of mass transport to and
from an electrode and, thus, causes an increase in the measured
electrical current. This increase is caused by an increase in the flow of
electrolyte solution past the working electrode, which is caused by
acoustic cavitation and/or acoustic streaming. This gives rise to what is
essentially hydrodynamic control of mass transport.

[0022]In a sonoelectrochemical system comprising an electrode-type
electrochemical system and an acoustic system, the steady state limiting
current (Ilim) may be described by equation (1):

I lim = nFACD δ [ 1 ] ##EQU00001##

where n is the number of electrons involved in the electrochemical
reaction, F is the Faraday constant, A is the area of the electrode, C is
the concentration of the electroactive species in bulk solution, D is the
diffusion coefficient of the electroactive species in the solution and
δ is the thickness of the stagnant diffusion layer between the
electrode and the bulk electrolyte solution. In experiments, values of
δ of one μm have been reported, which are considerably smaller
than values achieved under quiescent conditions. From experimentation and
analysis, some researchers have found that equation [1] may be expressed
as:

Ilim=nFACmi [2]

where mi is the average mass transport coefficient. In these
experiments, the researchers commented that mass transport rates achieved
by the application of high power ultrasound can be 100-1000 times greater
than with other hydrodynamic methods. For example, it has been noted that
a value of mi=0.0643 cm/s, which may be obtained by sonication in a
system comprising a combination of an ultrasound source and an electrode
system, could only be achieved by laminar flow in a rotating disk
electrode at a rotation speed of greater than 160,000 rpm, a value that
is not practically attainable.

[0023]The second advantage of the sonoelectrochemical system is that the
process of acoustic cavitation, namely the violent expansion and collapse
of gas bubbles within one acoustic cycle, can clean the electrode surface
and prevent passivation. The cleaning and erosion of solid surfaces by
high power ultrasound is often termed cavitational erosion. The
prevention or reduction of electrode fouling by the use of high power
ultrasound has enabled electrochemical measurements to be applied to the
analysis of a wide range of complex samples that would otherwise require
extensive sample preparation prior to the analysis. Sonoelectrochemical
measurements have been applied to a number of complex and potentially
fouling systems, including manganese in tea, copper in whole blood,
copper in beer, lead in human saliva, nitrite in eggs and the detection
of lead in water following extraction into an organic phase.

[0024]A critical aspect of sonoelectrochemical measurements is the
relative positioning of the acoustic horn that generates the high power
ultrasound and the working electrode. In general, up until now, the
commonest configuration has been to position the acoustic generator and
the working electrode face on with a separation of typically 1-30 mm This
configuration is cumbersome and small variations in the relative
positioning of the acoustic generator and working electrode can lead to
variations of up to factors of 15 in the measured currents. Consequently,
the accurate positioning of the acoustic generator relative to the
working electrode is essential for the determination of limiting
currents.

[0025]In a high power acoustic resonator, an acoustic horn may be used to
generate high power ultrasound. The high power acoustic resonator may
comprise an acoustic or ultrasonic (the words may be used interchangeably
herein) body, which may be referred to as an acoustic horn, which is a
mechanical device for amplifying the displacement and means of generating
a sinusoidal displacement--such as a piezoelectric or magnetostrictive
element. The displacement is generated by several piezoelectric elements
and the amplification of the displacement is achieved by the reduction in
cross-sectional area along the length of the horn, which is typically
made of a metal such as steel or titanium.

[0026]FIG. 1 shows a schematic of a high power acoustic resonator that may
be used in an embodiment of the present invention. Generally, a high
power acoustic resonator 10 may comprise an acoustic body/acoustic horn
15 (the terms acoustic body and acoustic horn may be used interchangeably
herein) attached to and/or incorporating an ultrasonic transducer 20. In
certain aspects, the ultrasonic transducer 20 may be disposed within or
coupled to a base 25 of the acoustic horn 15. A power source 19 may be
coupled with the ultrasonic transducer 20 to provide power to the
ultrasonic transducer 20. In an embodiment of the present invention, a
high power acoustic resonator with integrated electrode system may
consist of an ultrasonic piezoelectric transducer coupled to a suitable
metal horn.

[0027]In one aspect of such an embodiment, the piezoelectric transducer
may be configured to operate in a longitudinal mode. In such an aspect,
the resulting ultrasonic device may be characterized by having a sharp
resonant frequency, which can be conveniently determined by the
measurement of the admittance (or impedance) spectrum of the device.
Furthermore, the resonance frequency of the appropriate longitudinal mode
of such a device is sensitive to any solid deposit that forms on the tip
of the horn and the magnitude of the frequency shift is a measure of the
mass loading. The high power acoustic resonator 10 may comprise an
ultrasonic piezoelectric transducer coupled to a suitable metal horn and
may operate in the frequency range 10-250 kHz and may deliver high levels
of acoustic power, typically in the range 1-500 W, when driven by a high
input alternating voltage at its resonant frequency.

[0028]The acoustic horn may oscillate laterally or may be configured to
oscillate in a longitudinal mode. The resonant frequency of the acoustic
device operating in a longitudinal mode is determined by the thickness of
the piezoelectric, the acoustic horn 15 and the materials from which the
piezoelectric and acoustic horn 15 are constructed. The acoustic horn 15
may have a stepwise tapering design, an exponentially reducing diameter
or the like. The acoustic horn 15 may be made of titanium and have a
sharp resonant frequency in air of 40 kHz, where the area of the horn tip
is of the order 0.2 cm2. In some acoustic horn 15 designs, the
tapering is degenerated to a single step giving the acoustic horn 15 a
pin-like shape. Other horn shapes can be envisaged, including the case
where its thickness is very much less than the wavelength of sound and
the horn is a thin layer of material, for example but not by way of
limitation, that couples the ultrasonic transducer to the borehole fluids
and their deposits.

[0029]Acoustic horns are devices for generating high power ultrasound. An
acoustic (or ultrasonic) horn may consist of a means of generating a
sinusoidal displacement, such as a piezoelectric or magnetostrictive
element, and a mechanical device for amplifying the displacement. The
displacement of the acoustic horn may be generated by several
piezoelectric elements and the amplification of the displacement is
achieved by the reduction in cross-sectional area along the length of the
horn, which is typically made of a metal such as steel or titanium. The
horn is designed such that an anti-node is located at the tip of the horn
where the displacement is a maximum. When ultrasonic horns are operated
at high power levels, typically in excess of 10 W, the amplitude of the
displacement of the tip may be several tens of microns. Operation of the
ultrasonic horn at high power when the tip of the horn is immersed in
liquids at ambient pressure will give rise to acoustic cavitation in the
liquid and the flow of liquid away from the tip by a phenomenon known as
acoustic streaming. Acoustic cavitation in water at ambient pressure is
achieved at a power density in excess of 0.5-1.0 W per square centimeter
of horn tip and at a frequency of 20 kHz. In some embodiments of the
present invention, the acoustic horn 15 may comprise a base end 25 that
may provide a contact with the ultrasonic transducer 20 to provide for
the ultrasonic transducer 20 to vibrate the acoustic horn 15.

[0030]The resonant frequency of the acoustic device operating in a
longitudinal mode may be determined by the size of the ultrasonic
transducer 20 and the acoustic horn 15 and the materials from which the
ultrasonic transducer 20 and the acoustic horn 15 are constructed. The
design of the acoustic horn 15 may vary and may be a stepwise tapering, a
smooth tapering with an exponentially reducing diameter or the like. The
acoustic horn 15 may be designed such that the tapering is degenerated to
a single step giving the acoustic horn 15 a pin-like shape. Other horn
shapes can be envisaged, including the case where its thickness is very
much less than the wavelength of sound and the horn is a thin layer of
material that is coupled to the ultrasonic transducer 20. In embodiments
of the present invention, the design of the acoustic horn 15 may be such
as to amplify the acoustic energy onto the tip of the horn 17. In certain
aspects of the present invention, the acoustic horn 15 may be made of
titanium. Additionally, in certain aspects, the area of the horn tip 17
may be of the order of 0.2-2.0 cm2. In some embodiments of the
present invention, the length of the acoustic horn 15 is an odd integer
multiple N of half the wavelength (λ/2) of the acoustic wave
generated by the ultrasonic transducer 20.

[0031]FIG. 2 is a schematic-type diagram illustrating a high power
acoustic resonator with an integrated electrically conducting diamond
electrode, in accordance with an embodiment of the present invention. In
the depicted embodiment, a high power acoustic resonator with an
integrated electrically conducting diamond electrode 50 is illustrated.
The high power acoustic resonator with an integrated electrically
conducting diamond electrode 50 may comprise an acoustic horn 15, a base
60 and a transducer 65. In certain aspects, the transducer 65 may be
integrated into the base 60 and in other aspects; the transducer 65 may
be coupled with the base 60.

[0032]In an embodiment of the present invention, the high power acoustic
resonator with an integrated electrically conducting diamond electrode 50
may comprise an electrically conducting diamond electrode 70 disposed at
a tip 17 of the acoustic horn 15. In certain aspects, the single
electrically conducting diamond electrode 70 may comprise boron-doped
diamond. In the illustrated embodiment, the electrically conducting
diamond electrode 70 may be electrically isolated from the acoustic horn
15 by an isolating element 73. In certain aspects, the isolating element
73 may comprise non-conducting diamond.

[0033]In an embodiment of the present invention, a diamond substrate may
be located at the tip 17 of the acoustic horn 15, wherein the diamond
substrate may be of the order of about 1-10 millimeters in diameter and
comprise a ring of electrically non-conducting diamond with a central
disc approximately 0.5-5.0 millimeters wide of boron-doped diamond. This
diamond substrate may be formed by taking a diamond substrate and doping
a central region with boron.

[0034]The conductive diamond in the diamond substrate may be fabricated by
any method known to the art, but is preferably fabricated by doping
during growths and more preferably by doping with boron during growth. An
alternative method of creating the conductive diamond region or regions
is to use ion implantation. Alternative dopants may include other
substances capable of making the diamond substrate electrically
conductive.

[0035]An electrically conducting element 75, such as a copper or a silver
wire may be coupled with the electrically conducting diamond electrode
70. In alternative embodiments, the electrically conducting element 75
may comprise an electrically conducting channel or the like. In certain
aspects, the electrically conducting element 75 may be brazed to the back
of the electrically conducting diamond electrode using, for example, a
copper/silver/titanium active braze (e.g., EL-91 braze, made by Drijfhout
BV), which consists of a eutectic copper/silver wire (72 weight percent
silver) with a titanium core that constitutes approximately 10 weight
percent of the wire.

[0036]Merely by way of example, to provide for soldering/brazing using a
non-active solder/braze of the electrically conducting element 75 to the
electrically conducting diamond electrode 70, the back of the
electrically conducting diamond electrode 70 may be coated with a mixture
of elements such that they bond to diamond and yield a
solderable/brazeable surface. Merely by way of example, a method using
radio-frequency ("RF") bias sputtering may be employed to sputter
sequentially titanium, platinum and gold layers (approximately 0.1, 0.2
and 1.0 μm in thickness, respectively) onto the back of the
electrically conducting diamond electrode 70 using a mechanical masking
technique. The edge and rim of the isolating element 73 may also be
coated with the same titanium, platinum and gold layers by modifying the
mechanical mask to facilitate the mounting of the diamond electrode into
the recess in the tip of the acoustic horn 17, noting that the geometries
of the two metal layers must not generate any electrical contact between
the ultrasonic horn body 15 and the electrically conducting element 75
either after sputter coating or after bonding the isolating element 73
into the ultrasonic horn body 15. The tip of the ultrasonic horn 17 may
also be coated with the same titanium, platinum and gold layers to
facilitate the brazing/soldering of isolating element 73.

[0037]In some methods of constructing the sonoelectrochemical probe, the
electrically conducting diamond electrode 70 and/or the isolating element
73 may be soldered into a recess that may be created/machined into the
tip of acoustic horn 17. In such construction methods, the solder used
may have a lower melting point than the braze used to attach electrically
conducting element 75 to the electrically conducting diamond electrode
70. Merely by way of example, such braze may comprise the gold-germanium
eutectic, which consists of gold and germanium in the mole fraction ratio
of 0.88:0.12 and has a melting point of around 365 degrees Centigrade.
Care must be taken during such soldering to ensure that there is no
electrical short circuit created between the electrically conducting
diamond electrode and the acoustic horn 15. The electrically conducting
element 75 may be insulated from the acoustic horn 15 by surrounding the
electrically conducting element 75 with non-conducting tubing.

[0038]In one embodiment of the present invention, a central bolt 77 may be
disposed in or coupled with the base 60. The central bolt 77 may act to
provide access into an interior volume of the acoustic horn 15, provide
access to the back of the electrically conducting diamond electrode 70,
provide an anchoring point for the high power acoustic resonator with an
integrated electrically conducting diamond electrode 70, provide
stability for the high power acoustic resonator with an integrated
electrically conducting diamond electrode 70, and/or the like. In certain
aspects, the electrically conducting element 75 may be brought to the
interior/back of the acoustic horn 15 through a hole in the central bolt
77. Further, such integration in these embodiments may provide for a
self-contained high power acoustic resonator with the integrated
electrically conducting diamond electrode that may be suitable for use in
harsh conditions and/or for remote operations.

[0039]An alternative electrical connection to the electrically conducting
diamond electrode 70 may be made using wire bonding, which is a technique
much used in the integrated circuits industry Implementation of the wire
bonding technique may require the backside (the side that may be accessed
from the interior of the acoustic horn 15) of the electrically conducting
diamond electrode 70 to be coated with a mixture of elements chosen such
that they bond to diamond and give a wire-bondable surface. One such
combination of elements, for example, is achieved by layers of titanium,
platinum and gold (0.1, 0.2 and 1.0 μm in thickness, respectively),
which may be applied by sequential RF bias sputtering using
photolithographical techniques. Again, care must be taken that the
pattern coating is such a size and shape that there is no electrical
short circuit between the electrically conducting diamond electrode 70
and the acoustic horn 15 either before or after bonding the isolating
element 73 into the ultrasonic horn body 15.

[0040]FIG. 3 is a schematic-type diagram illustrating a high power
acoustic resonator with an integrated diamond electrode comprising a
plurality of conducting regions separated by non-conducting regions that
may be used as reference and/or counter and working electrodes, in
accordance with an embodiment of the present invention. In certain
embodiments of the present invention, the conducting-diamond electrode
may comprise a plurality of electrically conducting diamond electrodes,
illustrated in FIG. 3 as the electrically conducting diamond electrodes
101a, 101b and 101c, disposed in the tip 17 of the acoustic horn 15 with
at least one of the electrically conducting diamond electrodes 101a, 101b
and 101c being electrically isolated from the acoustic horn 15. In such
embodiments, one or more of the electrically conducting diamond
electrodes 101a, 101b and 101c may comprise boron-doped diamond. In
certain aspects, the acoustic horn 15 may comprise titanium.

[0041]In one embodiments of the present invention, the electrically
conducting diamond electrodes 101a, 101b and 101c may be arranged such
that the electrically conducting diamond electrodes 101a, 101b and 101c
and the tip 17 of the acoustic horn 15 are coplanar. In an alternative
embodiment, the electrically conducting diamond electrodes 101a, 101b and
101c may be disposed proximal to the tip 17. Such precise positioning of
the electrically conducting diamond electrodes 101a, 101b and 101c
relative to the tip illustrates one of the advantages of incorporating
the conductive elements and other interfaces between the electrically
conducting diamond electrodes 101a, 101b and 101c and elements external
to the sonoelectrochemical probe within the acoustic horn.

[0042]In the illustrated embodiment, the electrically conducting diamond
electrode 101a may comprise a disc surrounded by an electrically
insulating region 105a and 105b, where insulating regions 105a and 105b
may comprise a single ring of non-conducting material surrounding the
electrically conducting diamond electrode 101a. Similarly, electrically
conducting diamond electrodes 101b and 101c may comprise a single ring of
electrically conducting diamond and electrically insulating regions 105c
and 105d may comprise a single ring of electrically insulating material.
In certain aspects, the electrically conducting diamond electrodes 101a,
101b and 101c may comprise boron-doped diamond and the electrically
insulating regions 105a, 105b, 105c and 105d may comprise undoped
diamond. In a further embodiment, the number of electrically conducting
diamond and electrically insulating diamond rings may be increased so
long as the last diamond ring is electrically insulating.

[0043]Merely by way of example, in a sonoelectrochemical probe in
accordance with one embodiment of the present invention, a diamond
substrate may be located at the tip 17 and this substrate may have a
diameter of approximately 9 mm. This substrate may comprise a 2 mm
diameter central electrically conducting diamond electrode, which may be
used as a working electrode, and may be surrounded by concentric rings of
electrically non-conducting diamond alternating with concentric rings of
electrically conducting diamond. Since diamond is itself a non-conducting
substance, the concentric rings of electrically non-conducting diamond
may comprise diamond. The electrically conducting diamond rings may
comprise doped diamond where the dopant may be boron, phosphorus, sulfur
or the like, or any other dopant providing for electrical conduction by
the doped diamond. The concentric rings of the electrically conducting
diamond may have widths of the order of about 1-2 millimeters and, the
concentric rings of the electrically non-conducting diamond may have
widths of the order of 1-2 millimeters. In certain aspects, one of the
concentric rings of the electrically conducting diamond, which is
electrically insulated by the surrounding rings of non-conducting
diamond, may function as a counter electrode or a reference electrode in
an electrochemical circuit. In further aspects another electrically
conducting diamond ring, which is electrically insulated by the
surrounding rings of electrically non-conducting diamond, may function as
another reference electrode or counter electrode.

[0044]In an embodiment of the present invention, electrical contact with
one or more of the electrically conducting diamond electrodes 101a, 101b
and 101c may be made using electrically-conducting channels 117 that are
located in an insulating channel-support-matrix 115. In certain aspects,
the electrically conducting channels 117 and the insulating
channel-support-matrix 115 may comprise a drilled, solder-filled PCB
board or a laser drilled electrically non-conducting diamond plate filled
with an active metal braze. Merely by way of example, the
electrically-conducting channels 117 may have diameters of the order of
fractions of millimeters and the electrically-conducting channels 117 may
comprise channels in the insulating channel-support-matrix 115 that may
be filled with a mixture of copper, silver and titanium braze or the
like. The electrically conducting channels 117 may be positioned such
that one or more of the electrically conducting channels 117 is in
contact with one of the electrically conducting diamond electrodes 101a,
101b or 101c.

[0045]A plate may be used to help position and/or provide structural
support to the insulating channel-support-matrix 115 and diamond
electrode. In certain aspects, the plate 120 may comprise ceramic,
plastic or the like. The insulating channel-support-matrix 115 and the
electrically conducting channels 117 may be held in contact with the
underside of the electrode array, where the electrode array comprises the
electrically conducting diamond electrodes 101a, 101b or 101c and the
electrically insulating regions 105a, 105b, 105c and 105d, by a
mechanical support 120. The mechanical support 120 may include one or
more holes through which electrically conducting elements or channels
110a and 110b may pass and make contact with the electrically conducting
channels 117. The electrically conducting elements or channels 110a and
110b must not make electrical contact with the mechanical support 120
should the mechanical support 120 be made of an electrically conducting
material such as a metal.

[0046]In certain aspects, the electrically conducting element s or
channels 110a and 110b may be soldered or wire bonded to the electrically
conducting diamond electrodes 101a, 101b or 101c. Further, in certain
aspects, electrically conducting elements or channels 110a and 110b may
pass through and out of the acoustic horn 15 through a hole in the
central bolt 77 or the like. The electrically conducting elements or
channels 110a and 110b may be connected to electrical sources, processors
and/or the like to provide for operation and or analysis of one or more
of the electrically conducting diamond electrodes 101a, 101b or 101c. In
one embodiment of the present invention, the insulating
channel-support-matrix 115 and the mechanical support 120 may be machined
to provide that the insulating channel-support-matrix 115 and the
mechanical support 120 key mechanically into each other. In this way, the
orientation of the electrically conducting channels 117 and the one or
more holes in the mechanical support 120 may be maintained during
assembly.

[0047]In one embodiment of the present invention, a top surface of the
insulating channel-support-matrix 115 may be patterned with a metal layer
to provide for electrical contact to the underside of the one or more
electrically conducting diamond electrodes 101a, 101b or 101c, such metal
layer may comprise: (a) a standard copper layer, such as is used on a PCB
board, and may be applied to the insulating channel-support-matrix 115
using standard PCB patterning and etch techniques; (b) sequential layers
of titanium, platinum and gold and these layers may be applied to the
insulating channel-support-matrix 115 by RF bias sputtering using a
mechanical or photolithographical mask. Further, in some embodiments of
the present invention, the bottom surfaces of the electrically conducting
diamond electrodes 101a, 101b or 101c may be sequentially RF bias
sputtered with titanium, platinum and gold layers using a mechanical or
lithographic mask to provide that the pattern produced by the sputtering
matches the metal layer pattern on the insulating channel-support-matrix
115.

[0048]In certain fabrication methods, the acoustic horn 15 may comprise
two parts to allow for the electrode system to be assembled and the two
parts may be affixed together after the electrode system has been be
assembled. Affixation of the two parts may be provided by screws, bolts,
gluing, soldering, welding and/or the like.

[0049]In certain embodiments of the present invention, the one or more of
the electrically conducting diamond electrodes 101a, 101b or 101c
provided as a counter electrode may be configured in the electrical
arrangement to act as a second working electrode. In such embodiments, an
external counter may be utilized with the sonoelectrochemical probe. Such
configurations may provide for obtaining information about either the
electrochemical processes occurring at the working electrode(s) and/or
the flow of species across the electrically conducting diamond electrodes
101a, 101b or 101c.

[0050]FIG. 4 is a schematic-type diagram illustrating a high power
acoustic resonator with an integrated diamond electrode array, in
accordance with an embodiment of the present invention. In certain
aspects, the illustrated sonoelectrochemical probe 150 comprises a
diamond electrode array 155. The diamond electrode array 155 may comprise
a substrate across which may be an array of conducting and non-conducting
regions. In one aspect of the present invention, the substrate may
comprise diamond, the conducting regions may comprise doped diamond
regions and the non-conducting regions may comprise diamond. In such
embodiments, the doped diamond regions may be doped with a dopant such as
boron, phosphorous, sulfur, arsenic or the like. The diamond electrode
array 155 may be a macro-array and/or a micro-array.

[0051]Similar to the embodiment described in FIG. 3, the diamond electrode
array 155 may be supported by a non-conducting support layer (not shown)
through which conducting channels and/or elements may provide electrical
contact with the conducting regions of the diamond electrode array 155.
In some aspects of the present invention, a sapphire ring 165 may be
brazed into a recess in the acoustic horn 15 using techniques that may be
appreciated by those of skilled in the art. In such aspects, a portion of
a top surface of the sapphire ring 165 and a bottom surface of the
diamond electrode array 155 may both be coated with a mixture of elements
such that they bond to diamond and sapphire and yield brazeable surfaces.
This brazeable surface may comprise sequential metal layers of titanium,
platinum and gold that may be generated using an RF bias sputtering
technique with a mechanical mask or the like. In an embodiment of the
present invention, the diamond electrode array 155 may be soldered onto
the top surface of the sapphire ring 165. In certain aspects, the solder
used to solder the diamond electrode array 155 to the top surface of the
sapphire ring 165 may have a lower melting point than a braze, solder or
the like used to solder/braze the sapphire ring 165 to the acoustic horn
155.

[0052]In embodiments in which the diamond electrode array 155 is soldered
to the sapphire ring, the soldering may require careful positioning of
the diamond electrode array 155 to provide that an electrical short
circuit is not created between one or more of the conducting regions of
the diamond electrode array 155 and the acoustic horn 15. In certain
embodiments, a non-conducting adhesive 170 may be disposed at a gap
between the diamond electrode array 155 and the acoustic horn 15. The
non-conducting adhesive 170 may be a liquid non-conducting glue, such as
EPO-TEC 353ND epoxy, or the like. In certain fabrication methods for some
embodiments of the present invention, vacuum outgassing may be used to
provide for good penetration of the non-conducting adhesive 170 into the
gap prior to hardening.

[0053]In one embodiment of the present invention, electrical contact with
the diamond electrode array 155 may be made using a conductive element
185. In certain aspects, the conductive element 185 may be a gold-plated
pin or the like. The conductive element 185 may be disposed to provide
for contact with a rear-surface of the diamond electrode array 155. In
certain embodiments of the present invention, one or more non-conducting
plastic members 180a and 180b may be used keep an end of the conductive
element 185 in contact with the rear-surface of the diamond electrode
array 155. In one embodiment, a spring 160 may be used in conjunction
with the one or more non-conducting plastic members 180a and 180b to
provide for keeping the conductive element 185 in contact with the
rear-surface of the diamond electrode array 155. In certain aspects, the
one or more non-conducting plastic members 180a and 180b may be disposed
throughout the entire length of the inside of the acoustic horn 15 and
electrically conducting wires, electrically conducting channels and/or
the like may be disposed within the one or more non-conducting plastic
members 180a and 180b to provide that an electrical short circuit does
not occur.

[0054]In certain embodiments, as described in more detail with reference
to FIG. 3, the conductive element 185 may comprise one or more
electrically conducting elements or channels, an insulating
channel-support-matrix, a mechanical support and/or the like and may be
connected to a plurality of conducting wires of the like to provide for
selective electrical supply to and/or selective processing of one or more
of the conductive regions of the diamond electrode array 155.

[0055]In the foregoing description, for the purposes of illustration,
various methods and/or procedures were described in a particular order.
It should be appreciated that in alternate embodiments, the methods
and/or procedures may be performed in an order different than that
described. It should also be appreciated that the methods described above
may be performed by hardware components and/or may be embodied in
sequences of machine-executable instructions, which may be used to cause
a machine, such as a general-purpose or special-purpose processor or
logic circuits programmed with the instructions, to perform the methods.

[0056]Hence, while detailed descriptions of one or more embodiments of the
invention have been given above, various alternatives, modifications, and
equivalents will be apparent to those skilled in the art without varying
the invention. Moreover, except where clearly inappropriate or otherwise
expressly noted, it should be assumed that the features, devices and/or
components of different embodiments may be substituted and/or combined.
Thus, the above description should not be taken as limiting the scope of
the invention, which is defined by the appended claims.